<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        // 不是特别理解！
        let arr = [9, 3, 5, 8, 1, 6]
        function handleData(a, flag = true) {
            let sum = 0
            for (let i = 0; i < a.length; i++) {
                sum += a[i]
            }
            if (flag) {
                return sum
            } else {
                return sum / a.length
            }
        }
        console.log(handleData(arr,false));
    </script>
</body>

</html>